Kyoung Suk Kang

Photoluminescent carbon nanotags from harmful cyanobacteria for drug delivery and imaging in cancer cells

Using a simple method of mass production of green carbon nanotags (G-tags) from harmful cyanobacteria, we developed an advanced and efficient imaging platform for the purpose of anticancer therapy. Approximately 100 grams of G-tags per 100 kilograms of harmful cyanobacteria were prepared using our eco-friendly approach. The G-tags possess high solubility, excellent photostability, and low cytotoxicity (<1.5 mg/mL for 24 h). Moreover, doxorubicin-conjugated G-tags (T-tags; >0.1 mg/mL) induced death in cancer cells (HepG2 and MCF-7) in-vitro at a higher rate than that of only G-tags while in-vivo mice experiment showed enhanced anticancer efficacy by T-tags at 0.01 mg/mL, indicating that the loaded doxorubicin retains its pharmaceutical activity. The cancer cell uptake and intracellular location of the G- and T-tags were observed. The results indicate that these multifunctional T-tags can deliver doxorubicin to the targeted cancer cells and sense the delivery of doxorubicin by activating the fluorescence of G-tags.

Rapid and ultrasensitive detection of microRNA by target-assisted isothermal exponential amplification coupled with poly (thymine)-templated fluorescent copper nanoparticles.

We devised a novel method for rapid and ultrasensitive detection of target microRNA (miRNA) by employing target-assisted isothermal exponential amplification (TAIEA) combined with poly (thymine)-templated fluorescent copper nanoparticles (CuNPs) as signaling probes. The target miRNA hybridizes to the unimolecular template DNA and works as a primer for the extension reaction to form double-stranded product, which consequently generates two nicking endonuclease recognition sites. By simultaneous nicking and displacement reactions, exponential amplification generates many poly (thymine) strands as final products, which are employed for the synthesis of fluorescent CuNPs. Based on the fluorescent signal from CuNPs, target miRNA is detected as low as 0.27 fM around 1 h of total analysis time. The diagnostic capability of this system has been successfully demonstrated by reliably detecting target miRNA from different cell lysates, showing its great potential towards real clinical applications.

A simple and eco-friendly one-pot synthesis of nuclease-resistant DNA–inorganic hybrid nanoflowers

A simple and eco-friendly method has been developed for the one-pot synthesis of DNA-copper nanoflowers that exhibit high loading efficiencies, low cytotoxicities, and strong resistance against nucleases.

Aptamer-mediated universal enzyme assay based on target-triggered DNA polymerase activity

We herein describe an innovative method for a universal fluorescence turn-on enzyme assay, which relies on the target enzyme-triggered DNA polymerase activity. In the first target recognition step, the target enzyme is designed to destabilize detection probe derived from an aptamer specific to DNA polymerase containing the overhang sequence and the complementary blocker DNA, which consequently leads to the recovery of DNA polymerase activity inhibited by the detection probe. This target-triggered polymerase activity is monitored in the second signal transduction step based on primer extension reaction coupled with TaqMan probe. Utilizing this design principle, we have successfully detected the activities of two model enzymes, exonuclease I and uracil DNA glycosylase with high sensitivity and selectivity. Since this strategy is composed of separated target recognition and signal transduction modules, it could be universally employed for the sensitive determination of numerous different target enzymes by simply redesigning the overhang sequence of detection probe, while keeping TaqMan probe-based signal transduction module as a universal signaling tool.